#include <stdio.h>

int main()
{
    char a = -1;
    //原码10000000000000000000000000000001
    //补码11111111111111111111111111111111
    //存入11111111
    //提升为11111111111111111111111111111111
    signed char b = -1;
    //存入11111111
    //提升为11111111111111111111111111111111
    unsigned char c = -1;
    //存入11111111
    //提升为00000000000000000000000011111111
    printf("a = %d, b = %d, c = %d", a, b, c);
    return 0;
}